“Fat Thursday” in Christian Calendar is last Thursday before Great Post and also begins last week of carnival. This day is mostly celebrated in Poland and in Christian parts in Germany. The date depends from Easter, so Fat Thursday may be in different time every year. In these countries people eat with tradition donuts. According to legend “who doesn’t eat donut in this day, will not have success”…
“Mardi Gras” is called also as “Fat Tuesday”, “Pancake Tuesday” or “Shrove Thusday”, it’s last day before Ash Wednesday, last day of carnival and great occasion to eat freely pancake :) This day is celebrated in USA and United Kingdom.